1. Field of the Invention
The present disclosure relates to a system, a device, an assembly and a method for subcutaneous administration of therapeutic fluid and analyte sensing. More particularly, the present disclosure relates to a soft cannula and a flexible probe and a method for inserting the cannula or probe into the subcutaneous tissue and securing them to the skin. Even more particularly, the present disclosure relates to a cannula or probe that can be easily used with various infusion and sensing devices and mechanisms. Even more particularly, the present disclosure relates to a device for delivery of therapeutic fluid into the subcutaneous tissue and for sensing analytes, and a method for automatic or manual cannula or probe insertion with minimal skin pricking pain.
2. Background
Delivery of Therapeutic Fluids
Transcutaneous injection of therapeutic fluids is usually performed using a rigid (e.g., metal) hypodermic needle on occasion or periodically. Continuous administration of drugs is usually performed using a soft cannula that provides a passageway to the subcutaneous tissue and is connected to an infusion pump with long tubing (the cannula and tubing together are referred to as an “infusion set”). In a common form, the soft cannula is secured to the skin by a housing to include a self-sealing septum mounted at the proximal end of the cannula. The cannula may be initially assembled with an insertion needle (also referred to as “penetrating member”) extending through the septum and the cannula. The cannula and the housing can be inserted manually or automatically, as described, for example in U.S. Pat. No. 5,851,197, the content of which is hereby incorporated by reference in its entirety. After piercing the skin, the penetrating member is retracted leaving the soft cannula in place in the patient's subcutaneous compartment. The selected infusion device is then coupled to the cannula, typically by a tubing connected to the infusion pump to deliver the medication through the cannula to the patient. In some embodiments, the tubing is connected to the cannula housing at a distal location from the septum, as shown, for example, in U.S. Pat. Nos. 4,755,173, 5,176,662 and 5,257,980, the contents of which are hereby incorporated by reference in their entireties. In some embodiments, the infusion tubing is coupled to the cannula housing by, for example, an infusion needle that pierces the septum, as discussed, for example, in U.S. Pat. No. 5,522,803, the content of which is hereby incorporated by reference in its entirety. Subcutaneous infusion sets of the above-referenced type are used extensively to continuously deliver drugs such as insulin to the patient in programmable dosages, as discussed, for example, in U.S. Pat. Nos. 4,562,751, 4,685,903, 5,080,653 and 5,097,122, the contents of which are hereby incorporated by reference in their entireties. A soft cannula that provides a passageway to the subcutaneous tissue and is not connected to an infusion pump with long tubing is disclosed in U.S. Patent Application No. 2007/0135774, entitled “Fluid delivery devices, systems and methods”, the content of which is hereby incorporated by reference in its entirety. In the above-referenced device, the cannula and housing are rigidly connected to each other and the cannula is inserted manually into the body. After the penetrating member withdrawal, a rubber septum can be repetitively pierced by a needle of a common syringe. This device has some limitations:
1) manual insertion is painful and depends on user skills;
2) vertical insertion angle is generally the only angle feasible; and
3) the rubber septum has to be precisely pierced by the sharp metal needle, which is difficult to accomplish, especially when the device is attached to remote skin sites.
Sensing Bodily Analytes
Performance of continuous or periodic sensing operations of bodily analytes within the interstitial fluid of the subcutaneous (“SC”) tissue are discussed, for example, in U.S. Pat. Nos. 5,390,671, 5,391,250, 5,482,473, 5,299,571 and 6,565,509, the contents of which are hereby incorporated by reference in their entireties. Conventional sensing devices include a subcutaneous probe and a sensing unit that contains the processing unit. Insertion mechanisms and devices for SC probes are disclosed, for example, in U.S. Pat. No. 5,586,553, the content of which is hereby incorporated by reference in its entirety. The insertion set includes a penetrating member extending through a mounting base adapted for seated mounting onto the patient's skin. A flexible probe includes a proximal segment carried by the mounting base and a distal segment protruding from the mounting base and having one or more electrodes thereon. When the mounting base is pressed onto the patient's skin, the penetrating member pierces the skin to transcutaneously place the probe's distal segment therein. The penetrating member can then be withdrawn from the mounting base, leaving the probe's distal segment within the patient's body. The above-described probe insertion mechanism has several limitations:
1) the mounting base and the flexible probe are rigidly connected and therefore the insertion has to be performed manually or using a relatively bulky and expensive insertion device (“inserter”);
2) insertion is typically painful to the patient; and
3) generally, only one predetermined penetration angle is available.